Knife sharpener



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KNIFE SHARPENER Filed D00. 2, 1954 2 Sheets-Sheet l Afro/weis.

July 9, 1957 w. A. sPEAR ErAL KNIFE: SHARPENER- 2 Sheets-Sheet 2 Filed Dec. 2, `1954 I N V EN TORS A {Tom/5x5.

United States Patent O KNIFE SHARPENER Walter A. Spear and Lindol H. Sprague, Cincinnati, Uhio,

assignors to Nutone, Inc., Cincinnati, h10, a corporation of New York Application December 2, 1954, Serial No. 472,602

7 Claims. (Cl. 51-241) This invention relates to knife Sharpeners, and particularly to power driven knife Sharpeners which are designed for use in the home. More Specifically, the invention is directed to an improved knife sharpening wheel and means for mounting the wheel as an attachment to an electric motor unit of the type disclosed in copending patent applications Serial Nos. 409,371 and 409,372, both filed February 10, 1954.

The primary objective of the invention is to provide a knife Sharpener device which may be used by an unskilled person, such as the `average housewife, to put a keen edge on knives and other utensils without danger of burning the metal of which they are made.

The usual power operated knife Sharpener made for home use utilizes a rigid grinding wheel having a circumferentially disposed V groove, or its equivalent, formed therein, which groove is designed to receive the edge of the utensil to be sharpened. However, a considerable amount of Skill iS required in 'the use of such a Sharpener. The operator must hold the knife in a precise position relative to the groove and must apply the correct amount of pressure while running the knife back and forth in the groove, otherwise the knife is not sharpened properly. Then too, the unyielding surface of 'the grinding stone comprising the wheel is apt to cause burned spots in the edge of the knife if care is not exercised to move the knife continuously or if too much pressure is applied upon it.

In the preferred embodiment of the invention the sharpening wheel comprises a pair of exible, abrasive disks. The two disks are mounted upon a drive shaft face to face, but they are otherwise unsupported. The annular area of each disk adjacent to the periphery is angulated with respect to the plane of the disk such that when the two disks are placed face to face, a V groove is formed into which the blade of a knife may be inserted. When the exible disks are rotated at a high rate of speed, centrifugal force tends to hold the two disks into facial engagement with one another. Thus, when a knife to be sharpened is inserted between them, the abrasive disks are yieldingly held against the cutting edge by the centrifugal force on the spinning disks. It is found that the force tending to maintain the two disks in planar condition iS not sufficient to cause the metal of the knife to be overheated, but is Suiiicient to rapidly cut away the metal for a keen cutting edge.

The disks comprising the wheel, therefore, remove the factor of skill. Being flexible, they accommodate themselves to the shape and position of a knife blade inserted between them. Thus, regardless of the amount of downward pressure placed upon the knife, the spinning disks automatically form a V which conforms to the shape of the blade placed between them, and do so yieldingly while maintaining a safe pressure or cutting force against the edge being sharpened.

Other objects and advantages of the present invention will be readily apparent to those skilled in the art from ice 2 the following detailed description of the drawings in which:

Figure 1 is a side elevational view showing a preferred embodiment of the knife Sharpener attached to a motor unit.

Figure 2 is a longitudinal cross sectional view through the knife Sharpener and through a portion of the motor unit at the point of attachment of the Sharpener to the unit.

Figure 3 is a fragmentary cross sectional view taken on the line 3 3 in Figure 2.

Figure 4 is an exploded view Showing the parts of the resilient connector which is employed to connect the drive shaft of the Sharpener to the drive shaft of the motor unit.

Figure 5 is a diagrammatic cross sectional view taken on a plane which passes between the two cutter disks and showing a knife blade in position to be sharpened.

Figure 6 is a cross sectional view taken on the line 6--6 of Figure 5.

Figure 7 is a perspective view of one of the disks which are employed in the present Sharpener.

In the drawings, 'the numeral 10 designates an electric motor unit which is adapted to power the knife Sharpener of this invention. The housing of the motor unit is generally triangular in shape as viewed from an end. The motor itself is mounted within the central portion of the housing. The end Structure 11 at the left as viewed in Figure 1 encloses a speed reduction gear train for driving culinary attachments such as a mixer, the power take-off for these attachments is not shown. The end Structure 12 at the right end of the motor unit journals a high speed power take-olf shaft 13 to which the present sharpener is adapted to be attached. The details of the construction of Ithe motor unit shown are described in the two copending applications referred to above and for this reason it is believed to be unnecessary to describe them here. Additionally, it will be obvious that the knife Sharpener of the present invention is adapted to be used in conjunction with any source of high speed rotative force. i

The end structure 12 of the motor unit has a tapering socket 14 formed therein, which socket is adapted to receive a housing 15 for the present Sharpener device. The housing includes a short tapered casing 16 and an end cap 17. Generally, the casing 16 journals a drive shaft 18, whereas the end cap 17 encloses a pair of exible abrasive disks 19-19, which disks constitute the grinding wheel of the present Sharpener device.

More specifically, casing 16 comprises van outer wall 20 which is in the shape of a frustrum of a cone. The larger end of the casing has a circular annular flange 21 thereon which is adapted to seat snugly within the inner end of socket 14. The socket has three ribs designated 22 therein which may be formed as an integral part of the wall of the socket and which are spaced equally, circumferentially around the socket. These ribs are adapted to engage notches, such as the one designated 23, which are spaced equally about the periphery of flange 21. The ribs 22 in socket 14 stop short of the inner end of the socket by an amount equal to the thickness of flange 21. Thus, the Sharpener housing may be inserted into the Socket with the respective notches 23 engaging the ribs 22 and when seated snugly against the inner wall of the socket, the housing may be rotated so that the inner ends of the ribs overlie the outer edge of the ange. This prevents the housing from being withdrawn from the socket. To latch the housing in place in the socket, a small detent Spring 24 is provided, which spring is fastened to the casing by means of a bolt 25. The Spring extends outwardly from the wall of the casing and has the outer end thereof bent into an arc as at 26 to conform generally to the contour of the ribs 22. It will be noted that the arcuate portion 26 of the spring is offset with respect to the notch 23 in the flange 21, which is adjacent to the spring, so as to make contact with the adjacent rib when the housing is rotating slightly within socket 14. In addition, a pair of abutments 27 and 28 are provided on the Vouter face of flange 21. The rst of these abutments is positioned to stop rotation of the housing with respect to socket 14 when a rib 22 is engaged in the arcuate outer end of the spring. This constitutes the latched position of the housing. The other abutment, designated 28, is positioned to prevent the housing from being rotated in the wrong direction to engage the spring and rib.

Preferably, casing 16 is of cast construction, being made of a klight-weight metal such as aluminum or zinc alloy. The central longitudinal portion of the casing is coniigurated to provide a bearing journal 29. The journal may be supported by three webs such as the one shown at 30, which webs extend radially outwardly from the journal 29 to the outer wall 20 of the casing. The webs and the journal 29 should taper from the outer end of the casing toward the flanged end to facilitate removal of the cast body from the mold in production.

The end of the journal 29 toward the flanged end of the casing stops short to accommodate a flexible coupler f which is indicated generally at 31. This coupler includes a drive cup 32 which is adapted to be secured to the inner end of drive shaft 18. In the instance shown, the inner end of the shaft is square and is held in a square opening in the end wall of the drive cup by spinning or swaging over the end of the shaft. The drive cup 32 receives a resilient drive collar 33 which seats snugly inside of the cup. The drive collar is in the shape of a hollow cylinder, the inner diameter of which is adapted to receive a metal drive coupler 34. The drive coupler has an annular flange 35 at the outer end thereof. When seated in the drive collar, with the drive collar in the drive cup, the annular flange 35 is positioned to be embraced by the outer rim 36 of the drive cup which is swaged inwardly as shown in Figure 2. The drive coupler may have an octagonal socket 37 therein, which socket is adapted to receive the square outer end 38 of the high speed shaft 13 of the motor. The drive from the high speed shaft to drive shaft 18 therefore, is through the resilient drive collar 33 which adjusts for slight misalignment between the respective shafts 13 and 18.

The drive shaft 18 is journalled in a pair of bushings 39-39 which are seated within a bore 40 extending longitudinally through the center of journal 29. The outer end of the drive shaft extends beyond the casing 16 and into the hollow interior of the end cap or shell 17.V The outer end of shaft 18 as at 41 is of reduced diameter to mount the two flexible disks 19-19, each of which has a central opening 42 therein designed to fit the reduced end of the shaft. The two disks are seated upon the shaft in face to face relationship, with a pair of washers 43-43 engaged on the shaft at the opposite sides of the disks. The outer end of the shaft is threaded and a nut 44 engaged thereon, which nut may be tightened against a lock washer 45 residing against the outer one of the two washers 43--43. The shaft 18 is locked against endwise shifting movement within journal 29 by means of the nut 44. The bushing 39 at the inner end of journal 29 extends slightly beyond the inner end of the journal to provide clearance for the flexible coupler 31. At the opposite end ofthe journal, a spacer collar 46 is seated on the shaft, which spacer collar rides between the disks and the outer face of the other bushing 39 of the pair. When the nut 44 is tightened into place, the spacer and the coupler abut the respective bushings and thus prevent theY The thrust 'of the 4 present Sharpener device, are identical. In the preferred embodiment each disk is approximately 1% inches in diameter and made of cloth which is coated on one face with an adherent, closed coat of aluminum oxide. The grain size of the abrasive preferably is ne. The outer, annular, marginal portion of each disk is turned outwardly from the plane thereon in a direction away from the Y coated face. In this way when two disks are placed side by side, with their abrasive faces in Contact with one another, a V groove is provided, which groove is adapted to receive the blade of a knife to be sharpened. Preferably, the angulated outer marginal edge of each disk turns from theplane of the disk at a denite circle which may be formed by stamping so as to crease or at least compress the cloth. Such stamping causes a permanent deformation of the disk.

When rotated at high speed the centrifugal force on the two disks tend to hold them in facial contact with one another. This is aided by the two Washers 43-43 which back up the respective disks. The combination of the centrifugal force on the disks plus their yielding nature causes them to conform to the shape of a knife blade which is inserted between them, thus taking the factor of skill out of the sharpening operation.

The end cap 17 is slotted as at 47 to provide access to the disks. It will be noted that the slot 47Vextends over substantially 180 degrees of the upper half of the end cap and that it is wider at the top than it is at the bottom. The angulation of the slot permits the knife to be inserted into the V between the spinning disks parallel with the planes of the disks. Inserted in this way, a substantial wide marginal area of the cutting edge of the knife is exposed to the abrading surfaces on the spinning disks. The angulation of the slot also permits the knife to be inserted between the two disks in skew relationship to the plane of their abutting surfaces so that a lesser amount of the cutting edge is contacted by the disks. Hence, in this case, the ground edge does not extend as far onto the respective opposite sides of the blade.

Having described our invention, we claim:

l. 111 a knife Sharpener having a drive shaft adapted to be rotated at a high rate of speed, a pair of disks mounted upon said shaft for rotation therewith, each of said disks having an abrasive side, the two disks being disposed on the shaft with their respective abrasive sides toward one another, means in the central areas only of said disks to maintain said areas in tight facial engagement, each disk having an angulated rim portion such that a V is provided at the periphery of said disks for the insertion of a knife blade between said disks, and said disks being made of flexible sheet material and being unsupported in the respective outer annular areas, whereby they may yield to accommodate said knife blade between them.

2. In a knife Sharpener having a drive shaft adapted to be rotated at a high rate of speed, a pair of readily yieldable disks mounted upon said shaft for rotation therewith, each of said disks having an `abrasive coating on one side thereof, said disks disposed with their respective abrasive coated sides in facial engagement, the rim portion of each disk being turned at an angle to the plane of the disk such that a V is provided circumferentially of the two disks for the insertion of ya knife blade between them, and said disks being unsupported in their outer annular areas, whereby when they are rotated at a high rate of speed centrifugal force tends to hold them in yieldable facial engagement and thereby urges them against the respective opposite sides of a knife blade inserted between them.

3. A knife sharpening device adapted to be used as an attachment to a motor unit having a drive shaft, said knife sharpening device comprising a housing, a spindle rotatably journalled in said housing, a resilient coupler at one end of said spindle, means for attaching said device to said motor unit in position to engage said coupler with the drive shaft of said motor unit, a pair of exible disks mounted upon said spindle at the end thereof opposite to said coupler, each of said disks having an abrasive coating on one side thereof, said disks disposed with their respective abrasive sides in facial engagement, each disk having a rim portion thereof which is angulated such that a V is provided for the insertion of a knife blade between said disks 'and said flexible disks being unsupported in their respective outer annular areas whereby they may yield to accommodate said knife blade.

4. A knife sharpening device adapted to be used as an attachment to a motor unit, said knife sharpening device comprising a housing, a shaft rotatably journalled in said housing, means to removably attach said housing to said motor unit, means to couple said shaft to the drive shaft of said motor unit when said housing is attached thereto, a pair of abrasive disks mounted upon the rst named shaft for rotation therewith, the rim portion of each disk being angulated with respect to the plane of the disk such that a circumferential V is provided for the insertion of a knife blade between said disks, and said disks being readily flexible and being unsupported in their outer annular areas whereby they are adapted to yield upon the insertion of a knife blade between them.

5. A knife sharpening device adapted to be used as an attachment to a motor unit, said device comprising a housing, a shaft mounted for rotation in said housing, a flexible coupler at one end of said shaft, means to attach said housing to said motor unit such that the flexible coupler is engaged with the drive shaft of said motor unit, the end of the first named shaft opposite said coupler extending beyond said housing, a pair of abrasive cloth disks secured to the rst named shaft outside of said housing, each of said disks having the rim portion thereof `angulated with respect to the plane of the disk whereby a V is provided at the circumference `of the two disks for insertion of a knife blade between them, said disks being unsupported except in the central areas thereof immediately surrounding said rst named shaft, whereby the disks may yield to accommodate said knife blade, and a cap enclosing said disks, said cap being removably attached to said housing and having a slot at one side thereof to provide access for the insertion of said blade into said V.

6. In a knife Sharpener having a drive shaft adapted to be rotated at a high rate of speed, a pair of identical disks, each disk of the pair being made of readily exible sheet material having an Iabrasive coating 0n one face thereof, said disks disposed face to face with their respective abrasive coatings in contact with one another, the rim portion of each disk being angulated outwardly away from the face of the disk having the abrasive coating thereon such that a V is provided at the periphery of the two disks for the insertion of a knife blade between them, said disks being unsupported at their respective outer sides except in the central areas thereof immediately surrounding said shaft, whereby the outer marginal areas thereof may iiex outwardly with respect to one another upon the insertion of a knife blade between the disks to conform to the shape of the edge of said knife blade.

7. In a knife Sharpener having a drive shaft adapted to be rotated at a high rate of speed, said shaft having a threaded outer end `which is of a smaller diameter than the adjacent portion of the shaft to provide an annular shoulder, a pair of identical disks, each disk being made of readily exible sheet material having an abrasive coating on one face thereof, each disk having a central opening therein for engagement over the threaded end of said shaft, the respective disks being engaged upon the shaft, a nut tightened onto the threaded outer end of the shaft to press the central marginal areas of the two disks into tight contact with one another against said shoulder, the outer marginal edge of each disk being angulated outwardly from the plane of the disk, the two disks being disposed in face to face relation with their abrasive coatings in contact with one another and with their outer marginal areas deiiuing a V for the insertion of a knife blade between them, and the disks being unsupported except in their central portions by the shoulder and nut, whereby they may ilex outwardly away from one another to accommodate the knife blade between them.

References Cited in the file of this patent UNITED STATES PATENTS 440,948 Evans Nov. 18, 1890 594,320 Bonniwell Nov. 23, 1897 1,664,896 Perdue Apr. 3, 1928 1,983,011 Troll Dec. 4, 1934 2,129,538 Rubenstein et al. Sept. 6, 1938 2,146,548 Mitschang et al. Feb. 7, 1939 2,504,194 Harrington Apr. 18, 1950 2,616,231 Murray Nov. 4, 1952 

